SimpleCaptcha.php

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<?php
 
use MediaWiki\Auth\AuthenticationRequest;
 
class SimpleCaptcha {
    protected static $messagePrefix = 'captcha-';
 
    private $captchaSolved = null;
 
    protected $action;
 
    protected $trigger;
 
    public function setAction( $action ) {
        $this->action = $action;
    }
 
    public function setTrigger( $trigger ) {
        $this->trigger = $trigger;
    }
 
    public function getError() {
        return null;
    }
 
    public function getCaptcha() {
        $a = mt_rand( 0, 100 );
        $b = mt_rand( 0, 10 );
 
        /* Minus sign is used in the question. UTF-8,
           since the api uses text/plain, not text/html */
        $op = mt_rand( 0, 1 ) ? '+' : '−';
 
        // No space before and after $op, to ensure correct
        // directionality.
        $test = "$a$op$b";
        $answer = ( $op == '+' ) ? ( $a + $b ) : ( $a - $b );
        return [ 'question' => $test, 'answer' => $answer ];
    }
 
    protected function addCaptchaAPI( &$resultArr ) {
        $captcha = $this->getCaptcha();
        $index = $this->storeCaptcha( $captcha );
        $resultArr['captcha'] = $this->describeCaptchaType();
        $resultArr['captcha']['id'] = $index;
        $resultArr['captcha']['question'] = $captcha['question'];
    }
 
    public function describeCaptchaType() {
        return [
            'type' => 'simple',
            'mime' => 'text/plain',
        ];
    }
 
    public function getFormInformation( $tabIndex = 1 ) {
        $captcha = $this->getCaptcha();
        $index = $this->storeCaptcha( $captcha );
 
        return [
            'html' =>
                new OOUI\FieldLayout(
                    new OOUI\NumberInputWidget( [
                        'name' => 'wpCaptchaWord',
                        'classes' => [ 'simplecaptcha-answer' ],
                        'id' => 'wpCaptchaWord',
                        'autocomplete' => 'off',
                        // tab in before the edit textarea
                        'tabIndex' => $tabIndex
                    ] ),
                    [
                        'align' => 'left',
                        'label' => $captcha['question'] . ' = ',
                        'classes' => [ 'simplecaptcha-field' ],
                    ]
                ) .
                new OOUI\HiddenInputWidget( [
                    'name' => 'wpCaptchaId',
                    'id' => 'wpCaptchaId',
                    'value' => $index
                ] ),
            'modulestyles' => [
                'ext.confirmEdit.simpleCaptcha'
            ]
        ];
    }
 
    public function addFormToOutput( OutputPage $out, $tabIndex = 1 ) {
        $this->addFormInformationToOutput( $out, $this->getFormInformation( $tabIndex ) );
    }
 
    public function addFormInformationToOutput( OutputPage $out, array $formInformation ) {
        if ( !$formInformation ) {
            return;
        }
        if ( isset( $formInformation['html'] ) ) {
            $out->addHTML( $formInformation['html'] );
        }
        if ( isset( $formInformation['modules'] ) ) {
            $out->addModules( $formInformation['modules'] );
        }
        if ( isset( $formInformation['modulestyles'] ) ) {
            $out->addModuleStyles( $formInformation['modulestyles'] );
        }
        if ( isset( $formInformation['headitems'] ) ) {
            $out->addHeadItems( $formInformation['headitems'] );
        }
    }
 
    public function getCaptchaInfo( $captchaData, $id ) {
        return $captchaData['question'] . ' =';
    }
 
    public function showEditFormFields( &$editPage, &$out ) {
        $page = $editPage->getArticle()->getPage();
        if ( !isset( $page->ConfirmEdit_ActivateCaptcha ) ) {
            return;
        }
 
        if ( $this->action !== 'edit' ) {
            unset( $page->ConfirmEdit_ActivateCaptcha );
            $out->addHTML( $this->getMessage( $this->action )->parseAsBlock() );
            $this->addFormToOutput( $out );
        }
    }
 
    public function editShowCaptcha( $editPage ) {
        $context = $editPage->getArticle()->getContext();
        $page = $editPage->getArticle()->getPage();
        $out = $context->getOutput();
        if ( isset( $page->ConfirmEdit_ActivateCaptcha ) ||
            $this->shouldCheck( $page, '', '', $context )
        ) {
            $out->addHTML( $this->getMessage( $this->action )->parseAsBlock() );
            $this->addFormToOutput( $out );
        }
        unset( $page->ConfirmEdit_ActivateCaptcha );
    }
 
    public function getMessage( $action ) {
        // one of captcha-edit, captcha-addurl, captcha-badlogin, captcha-createaccount,
        // captcha-create, captcha-sendemail
        $name = static::$messagePrefix . $action;
        $msg = wfMessage( $name );
        // obtain a more tailored message, if possible, otherwise, fall back to
        // the default for edits
        return $msg->isDisabled() ? wfMessage( static::$messagePrefix . 'edit' ) : $msg;
    }
 
    public function injectEmailUser( &$form ) {
        $out = $form->getOutput();
        $user = $form->getUser();
        if ( $this->triggersCaptcha( CaptchaTriggers::SENDEMAIL ) ) {
            $this->action = 'sendemail';
            if ( $this->canSkipCaptcha( $user, $form->getConfig() ) ) {
                return true;
            }
            $formInformation = $this->getFormInformation();
            $formMetainfo = $formInformation;
            unset( $formMetainfo['html'] );
            $this->addFormInformationToOutput( $out, $formMetainfo );
            $form->addFooterText(
                "<div class='captcha'>" .
                $this->getMessage( 'sendemail' )->parseAsBlock() .
                $formInformation['html'] .
                "</div>\n" );
        }
        return true;
    }
 
    public function increaseBadLoginCounter( $username ) {
        global $wgCaptchaBadLoginExpiration, $wgCaptchaBadLoginPerUserExpiration;
 
        $cache = ObjectCache::getLocalClusterInstance();
 
        if ( $this->triggersCaptcha( CaptchaTriggers::BAD_LOGIN ) ) {
            $key = $this->badLoginKey();
            $count = ObjectCache::getLocalClusterInstance()->get( $key );
            if ( !$count ) {
                $cache->add( $key, 0, $wgCaptchaBadLoginExpiration );
            }
 
            $cache->incr( $key );
        }
 
        if ( $this->triggersCaptcha( CaptchaTriggers::BAD_LOGIN_PER_USER ) && $username ) {
            $key = $this->badLoginPerUserKey( $username );
            $count = $cache->get( $key );
            if ( !$count ) {
                $cache->add( $key, 0, $wgCaptchaBadLoginPerUserExpiration );
            }
 
            $cache->incr( $key );
        }
    }
 
    public function resetBadLoginCounter( $username ) {
        if ( $this->triggersCaptcha( CaptchaTriggers::BAD_LOGIN_PER_USER ) && $username ) {
            $cache = ObjectCache::getLocalClusterInstance();
            $cache->delete( $this->badLoginPerUserKey( $username ) );
        }
    }
 
    public function isBadLoginTriggered() {
        global $wgCaptchaBadLoginAttempts;
 
        $cache = ObjectCache::getLocalClusterInstance();
        return $this->triggersCaptcha( CaptchaTriggers::BAD_LOGIN )
            && (int)$cache->get( $this->badLoginKey() ) >= $wgCaptchaBadLoginAttempts;
    }
 
    public function isBadLoginPerUserTriggered( $u ) {
        global $wgCaptchaBadLoginPerUserAttempts;
 
        $cache = ObjectCache::getLocalClusterInstance();
 
        if ( is_object( $u ) ) {
            $u = $u->getName();
        }
        return $this->triggersCaptcha( CaptchaTriggers::BAD_LOGIN_PER_USER )
            && (int)$cache->get( $this->badLoginPerUserKey( $u ) ) >= $wgCaptchaBadLoginPerUserAttempts;
    }
 
    private function isIPWhitelisted() {
        global $wgCaptchaWhitelistIP, $wgRequest;
        $ip = $wgRequest->getIP();
 
        if ( $wgCaptchaWhitelistIP ) {
            if ( IP::isInRanges( $ip, $wgCaptchaWhitelistIP ) ) {
                return true;
            }
        }
 
        $whitelistMsg = wfMessage( 'captcha-ip-whitelist' )->inContentLanguage();
        if ( !$whitelistMsg->isDisabled() ) {
            $whitelistedIPs = $this->getWikiIPWhitelist( $whitelistMsg );
            if ( IP::isInRanges( $ip, $whitelistedIPs ) ) {
                return true;
            }
        }
 
        return false;
    }
 
    private function getWikiIPWhitelist( Message $msg ) {
        $cache = ObjectCache::getMainWANInstance();
        $cacheKey = $cache->makeKey( 'confirmedit', 'ipwhitelist' );
 
        $cachedWhitelist = $cache->get( $cacheKey );
        if ( $cachedWhitelist === false ) {
            // Could not retrieve from cache so build the whitelist directly
            // from the wikipage
            $whitelist = $this->buildValidIPs(
                explode( "\n", $msg->plain() )
            );
            // And then store it in cache for one day. This cache is cleared on
            // modifications to the whitelist page.
            // @see ConfirmEditHooks::onPageContentSaveComplete()
            $cache->set( $cacheKey, $whitelist, 86400 );
        } else {
            // Whitelist from the cache
            $whitelist = $cachedWhitelist;
        }
 
        return $whitelist;
    }
 
    private function buildValidIPs( array $input ) {
        // Remove whitespace and blank lines first
        $ips = array_map( 'trim', $input );
        $ips = array_filter( $ips );
 
        $validIPs = [];
        foreach ( $ips as $ip ) {
            if ( IP::isIPAddress( $ip ) ) {
                $validIPs[] = $ip;
            }
        }
 
        return $validIPs;
    }
 
    private function badLoginKey() {
        global $wgRequest;
        $ip = $wgRequest->getIP();
        return wfGlobalCacheKey( 'captcha', 'badlogin', 'ip', $ip );
    }
 
    private function badLoginPerUserKey( $username ) {
        $username = User::getCanonicalName( $username, 'usable' ) ?: $username;
        return wfGlobalCacheKey( 'captcha', 'badlogin', 'user', md5( $username ) );
    }
 
    protected function keyMatch( $answer, $info ) {
        return $answer == $info['answer'];
    }
 
    // ----------------------------------
 
    public function captchaTriggers( $title, $action ) {
        return $this->triggersCaptcha( $action, $title );
    }
 
    public function triggersCaptcha( $action, $title = null ) {
        global $wgCaptchaTriggers, $wgCaptchaTriggersOnNamespace;
 
        $result = false;
        $triggers = $wgCaptchaTriggers;
        $attributeCaptchaTriggers = ExtensionRegistry::getInstance()
            ->getAttribute( CaptchaTriggers::EXT_REG_ATTRIBUTE_NAME );
        if ( is_array( $attributeCaptchaTriggers ) ) {
            $triggers += $attributeCaptchaTriggers;
        }
 
        if ( isset( $triggers[$action] ) ) {
            $result = $triggers[$action];
        }
 
        if (
            $title !== null &&
            isset( $wgCaptchaTriggersOnNamespace[$title->getNamespace()][$action] )
        ) {
            $result = $wgCaptchaTriggersOnNamespace[$title->getNamespace()][$action];
        }
 
        return $result;
    }
 
    public function shouldCheck( WikiPage $page, $content, $section, $context, $oldtext = null ) {
        if ( !$context instanceof IContextSource ) {
            $context = RequestContext::getMain();
        }
 
        $request = $context->getRequest();
        $user = $context->getUser();
 
        if ( $this->canSkipCaptcha( $user, $context->getConfig() ) ) {
            return false;
        }
 
        $title = $page->getTitle();
        $this->trigger = '';
 
        if ( $content instanceof Content ) {
            if ( $content->getModel() == CONTENT_MODEL_WIKITEXT ) {
                $newtext = $content->getNativeData();
            } else {
                $newtext = null;
            }
            $isEmpty = $content->isEmpty();
        } else {
            $newtext = $content;
            $isEmpty = $content === '';
        }
 
        if ( $this->triggersCaptcha( 'edit', $title ) ) {
            // Check on all edits
            $this->trigger = sprintf( "edit trigger by '%s' at [[%s]]",
                $user->getName(),
                $title->getPrefixedText() );
            $this->action = 'edit';
            wfDebug( "ConfirmEdit: checking all edits...\n" );
            return true;
        }
 
        if ( $this->triggersCaptcha( 'create', $title ) && !$title->exists() ) {
            // Check if creating a page
            $this->trigger = sprintf( "Create trigger by '%s' at [[%s]]",
                $user->getName(),
                $title->getPrefixedText() );
            $this->action = 'create';
            wfDebug( "ConfirmEdit: checking on page creation...\n" );
            return true;
        }
 
        // The following checks are expensive and should be done only,
        // if we can assume, that the edit will be saved
        if ( !$request->wasPosted() ) {
            wfDebug(
                "ConfirmEdit: request not posted, assuming that no content will be saved -> no CAPTCHA check"
            );
            return false;
        }
 
        if ( !$isEmpty && $this->triggersCaptcha( 'addurl', $title ) ) {
            // Only check edits that add URLs
            if ( $content instanceof Content ) {
                // Get links from the database
                $oldLinks = $this->getLinksFromTracker( $title );
                // Share a parse operation with Article::doEdit()
                $editInfo = $page->prepareContentForEdit( $content );
                if ( $editInfo->output ) {
                    $newLinks = array_keys( $editInfo->output->getExternalLinks() );
                } else {
                    $newLinks = [];
                }
            } else {
                // Get link changes in the slowest way known to man
                if ( $oldtext === null ) {
                    $oldtext = $this->loadText( $title, $section );
                }
                $oldLinks = $this->findLinks( $title, $oldtext );
                $newLinks = $this->findLinks( $title, $newtext );
            }
 
            $unknownLinks = array_filter( $newLinks, [ $this, 'filterLink' ] );
            $addedLinks = array_diff( $unknownLinks, $oldLinks );
            $numLinks = count( $addedLinks );
 
            if ( $numLinks > 0 ) {
                $this->trigger = sprintf( "%dx url trigger by '%s' at [[%s]]: %s",
                    $numLinks,
                    $user->getName(),
                    $title->getPrefixedText(),
                    implode( ", ", $addedLinks ) );
                $this->action = 'addurl';
                return true;
            }
        }
 
        global $wgCaptchaRegexes;
        if ( $newtext !== null && $wgCaptchaRegexes ) {
            if ( !is_array( $wgCaptchaRegexes ) ) {
                throw new UnexpectedValueException(
                    '$wgCaptchaRegexes is required to be an array, ' . gettype( $wgCaptchaRegexes ) . ' given.'
                );
            }
            // Custom regex checks. Reuse $oldtext if set above.
            if ( $oldtext === null ) {
                $oldtext = $this->loadText( $title, $section );
            }
 
            foreach ( $wgCaptchaRegexes as $regex ) {
                $newMatches = [];
                if ( preg_match_all( $regex, $newtext, $newMatches ) ) {
                    $oldMatches = [];
                    preg_match_all( $regex, $oldtext, $oldMatches );
 
                    $addedMatches = array_diff( $newMatches[0], $oldMatches[0] );
 
                    $numHits = count( $addedMatches );
                    if ( $numHits > 0 ) {
                        $this->trigger = sprintf( "%dx %s at [[%s]]: %s",
                            $numHits,
                            $regex,
                            $user->getName(),
                            $title->getPrefixedText(),
                            implode( ", ", $addedMatches ) );
                        $this->action = 'edit';
                        return true;
                    }
                }
            }
        }
 
        return false;
    }
 
    private function filterLink( $url ) {
        global $wgCaptchaWhitelist;
        static $regexes = null;
 
        if ( $regexes === null ) {
            $source = wfMessage( 'captcha-addurl-whitelist' )->inContentLanguage();
 
            $regexes = $source->isDisabled()
                ? []
                : $this->buildRegexes( explode( "\n", $source->plain() ) );
 
            if ( $wgCaptchaWhitelist !== false ) {
                array_unshift( $regexes, $wgCaptchaWhitelist );
            }
        }
 
        foreach ( $regexes as $regex ) {
            if ( preg_match( $regex, $url ) ) {
                return false;
            }
        }
 
        return true;
    }
 
    private function buildRegexes( $lines ) {
        # Code duplicated from the SpamBlacklist extension (r19197)
        # and later modified.
 
        # Strip comments and whitespace, then remove blanks
        $lines = array_filter( array_map( 'trim', preg_replace( '/#.*$/', '', $lines ) ) );
 
        # No lines, don't make a regex which will match everything
        if ( count( $lines ) == 0 ) {
            wfDebug( "No lines\n" );
            return [];
        } else {
            # Make regex
            # It's faster using the S modifier even though it will usually only be run once
            // $regex = 'http://+[a-z0-9_\-.]*(' . implode( '|', $lines ) . ')';
            // return '/' . str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $regex) ) . '/Si';
            $regexes = [];
            $regexStart = [
                'normal' => '/^(?:https?:)?\/\/+[a-z0-9_\-.]*(?:',
                'noprotocol' => '/^(?:',
            ];
            $regexEnd = [
                'normal' => ')/Si',
                'noprotocol' => ')/Si',
            ];
            $regexMax = 4096;
            $build = [];
            foreach ( $lines as $line ) {
                # Extract flags from the line
                $options = [];
                if ( preg_match( '/^(.*?)\s*<([^<>]*)>$/', $line, $matches ) ) {
                    if ( $matches[1] === '' ) {
                        wfDebug( "Line with empty regex\n" );
                        continue;
                    }
                    $line = $matches[1];
                    $opts = preg_split( '/\s*\|\s*/', trim( $matches[2] ) );
                    foreach ( $opts as $opt ) {
                        $opt = strtolower( $opt );
                        if ( $opt == 'noprotocol' ) {
                            $options['noprotocol'] = true;
                        }
                    }
                }
 
                $key = isset( $options['noprotocol'] ) ? 'noprotocol' : 'normal';
 
                // FIXME: not very robust size check, but should work. :)
                if ( !isset( $build[$key] ) ) {
                    $build[$key] = $line;
                } elseif ( strlen( $build[$key] ) + strlen( $line ) > $regexMax ) {
                    $regexes[] = $regexStart[$key] .
                        str_replace( '/', '\/', preg_replace( '|\\\*/|', '/', $build[$key] ) ) .
                        $regexEnd[$key];
                    $build[$key] = $line;
                } else {
                    $build[$key] .= '|' . $line;
                }
            }
            foreach ( $build as $key => $value ) {
                $regexes[] = $regexStart[$key] .
                    str_replace( '/', '\/', preg_replace( '|\\\*/|', '/', $build[$key] ) ) .
                    $regexEnd[$key];
            }
            return $regexes;
        }
    }
 
    private function getLinksFromTracker( $title ) {
        $dbr = wfGetDB( DB_REPLICA );
        // should be zero queries
        $id = $title->getArticleID();
        $res = $dbr->select( 'externallinks', [ 'el_to' ],
            [ 'el_from' => $id ], __METHOD__ );
        $links = [];
        foreach ( $res as $row ) {
            $links[] = $row->el_to;
        }
        return $links;
    }
 
    private function doConfirmEdit( WikiPage $page, $newtext, $section, IContextSource $context ) {
        global $wgUser, $wgRequest;
        $request = $context->getRequest();
 
        // FIXME: Stop using wgRequest in other parts of ConfirmEdit so we can
        // stop having to duplicate code for it.
        if ( $request->getVal( 'captchaid' ) ) {
            $request->setVal( 'wpCaptchaId', $request->getVal( 'captchaid' ) );
            $wgRequest->setVal( 'wpCaptchaId', $request->getVal( 'captchaid' ) );
        }
        if ( $request->getVal( 'captchaword' ) ) {
            $request->setVal( 'wpCaptchaWord', $request->getVal( 'captchaword' ) );
            $wgRequest->setVal( 'wpCaptchaWord', $request->getVal( 'captchaword' ) );
        }
        if ( $this->shouldCheck( $page, $newtext, $section, $context ) ) {
            return $this->passCaptchaLimitedFromRequest( $wgRequest, $wgUser );
        } else {
            wfDebug( "ConfirmEdit: no need to show captcha.\n" );
            return true;
        }
    }
 
    public function confirmEditMerged( $context, $content, $status, $summary, $user, $minorEdit ) {
        if ( !$context->canUseWikiPage() ) {
            // we check WikiPage only
            // try to get an appropriate title for this page
            $title = $context->getTitle();
            if ( $title instanceof Title ) {
                $title = $title->getFullText();
            } else {
                // otherwise it's an unknown page where this function is called from
                $title = 'unknown';
            }
            // log this error, it could be a problem in another extension,
            // edits should always have a WikiPage if
            // they go through EditFilterMergedContent.
            wfDebug( __METHOD__ . ': Skipped ConfirmEdit check: No WikiPage for title ' . $title );
            return true;
        }
        $page = $context->getWikiPage();
        if ( !$this->doConfirmEdit( $page, $content, false, $context ) ) {
            $status->value = EditPage::AS_HOOK_ERROR_EXPECTED;
            $status->apiHookResult = [];
            // give an error message for the user to know, what goes wrong here.
            // this can't be done for addurl trigger, because this requires one "free" save
            // for the user, which we don't know, when he did it.
            if ( $this->action === 'edit' ) {
                $status->fatal(
                    new RawMessage(
                        Html::element(
                            'div',
                            [ 'class' => 'errorbox' ],
                            $context->msg( 'captcha-edit-fail' )->text()
                        )
                    )
                );
            }
            $this->addCaptchaAPI( $status->apiHookResult );
            $page->ConfirmEdit_ActivateCaptcha = true;
            return false;
        }
        return true;
    }
 
    public function needCreateAccountCaptcha( User $creatingUser = null ) {
        global $wgUser;
        $creatingUser = $creatingUser ?: $wgUser;
 
        if ( $this->triggersCaptcha( CaptchaTriggers::CREATE_ACCOUNT ) ) {
            if ( $this->canSkipCaptcha( $creatingUser,
                \MediaWiki\MediaWikiServices::getInstance()->getMainConfig() ) ) {
                return false;
            }
            return true;
        }
        return false;
    }
 
    public function confirmEmailUser( $from, $to, $subject, $text, &$error ) {
        global $wgUser, $wgRequest;
 
        if ( $this->triggersCaptcha( CaptchaTriggers::SENDEMAIL ) ) {
            if ( $this->canSkipCaptcha( $wgUser,
                \MediaWiki\MediaWikiServices::getInstance()->getMainConfig() ) ) {
                return true;
            }
 
            if ( defined( 'MW_API' ) ) {
                # API mode
                # Asking for captchas in the API is really silly
                $error = Status::newFatal( 'captcha-disabledinapi' );
                return false;
            }
            $this->trigger = "{$wgUser->getName()} sending email";
            if ( !$this->passCaptchaLimitedFromRequest( $wgRequest, $wgUser ) ) {
                $error = Status::newFatal( 'captcha-sendemail-fail' );
                return false;
            }
        }
        return true;
    }
 
    protected function isAPICaptchaModule( $module ) {
        return $module instanceof ApiEditPage;
    }
 
    public function apiGetAllowedParams( &$module, &$params, $flags ) {
        if ( $this->isAPICaptchaModule( $module ) ) {
            $params['captchaword'] = [
                ApiBase::PARAM_HELP_MSG => 'captcha-apihelp-param-captchaword',
            ];
            $params['captchaid'] = [
                ApiBase::PARAM_HELP_MSG => 'captcha-apihelp-param-captchaid',
            ];
        }
 
        return true;
    }
 
    public function passCaptchaLimitedFromRequest( WebRequest $request, User $user ) {
        list( $index, $word ) = $this->getCaptchaParamsFromRequest( $request );
        return $this->passCaptchaLimited( $index, $word, $user );
    }
 
    protected function getCaptchaParamsFromRequest( WebRequest $request ) {
        $index = $request->getVal( 'wpCaptchaId' );
        $word = $request->getVal( 'wpCaptchaWord' );
        return [ $index, $word ];
    }
 
    public function passCaptchaLimited( $index, $word, User $user ) {
        // don't increase pingLimiter here, just check, if CAPTCHA limit exceeded
        if ( $user->pingLimiter( 'badcaptcha', 0 ) ) {
            // for debugging add an proper error message, the user just see an false captcha error message
            $this->log( 'User reached RateLimit, preventing action' );
            return false;
        }
 
        if ( $this->passCaptcha( $index, $word ) ) {
            return true;
        }
 
        // captcha was not solved: increase limit and return false
        $user->pingLimiter( 'badcaptcha' );
        return false;
    }
 
    public function passCaptchaFromRequest( WebRequest $request, User $user ) {
        list( $index, $word ) = $this->getCaptchaParamsFromRequest( $request );
        return $this->passCaptcha( $index, $word );
    }
 
    protected function passCaptcha( $index, $word ) {
        // Don't check the same CAPTCHA twice in one session,
        // if the CAPTCHA was already checked - Bug T94276
        if ( isset( $this->captchaSolved ) ) {
            return $this->captchaSolved;
        }
 
        $info = $this->retrieveCaptcha( $index );
        if ( $info ) {
            if ( $this->keyMatch( $word, $info ) ) {
                $this->log( "passed" );
                $this->clearCaptcha( $index );
                $this->captchaSolved = true;
                return true;
            } else {
                $this->clearCaptcha( $index );
                $this->log( "bad form input" );
                $this->captchaSolved = false;
                return false;
            }
        } else {
            $this->log( "new captcha session" );
            return false;
        }
    }
 
    protected function log( $message ) {
        wfDebugLog( 'captcha', 'ConfirmEdit: ' . $message . '; ' . $this->trigger );
    }
 
    public function storeCaptcha( $info ) {
        if ( !isset( $info['index'] ) ) {
            // Assign random index if we're not udpating
            $info['index'] = strval( mt_rand() );
        }
        CaptchaStore::get()->store( $info['index'], $info );
        return $info['index'];
    }
 
    public function retrieveCaptcha( $index ) {
        return CaptchaStore::get()->retrieve( $index );
    }
 
    public function clearCaptcha( $index ) {
        CaptchaStore::get()->clear( $index );
    }
 
    private function loadText( $title, $section, $flags = Revision::READ_LATEST ) {
        global $wgParser;
 
        $rev = Revision::newFromTitle( $title, false, $flags );
        if ( is_null( $rev ) ) {
            return "";
        }
 
        $content = $rev->getContent();
        $text = ContentHandler::getContentText( $content );
        if ( $section !== '' ) {
            return $wgParser->getSection( $text, $section );
        }
 
        return $text;
    }
 
    private function findLinks( $title, $text ) {
        global $wgParser, $wgUser;
 
        $options = new ParserOptions();
        $text = $wgParser->preSaveTransform( $text, $title, $wgUser, $options );
        $out = $wgParser->parse( $text, $title, $options );
 
        return array_keys( $out->getExternalLinks() );
    }
 
    public function showHelp() {
        global $wgOut;
        $wgOut->setPageTitle( wfMessage( 'captchahelp-title' )->text() );
        $wgOut->addWikiMsg( 'captchahelp-text' );
        if ( CaptchaStore::get()->cookiesNeeded() ) {
            $wgOut->addWikiMsg( 'captchahelp-cookies-needed' );
        }
    }
 
    public function createAuthenticationRequest() {
        $captchaData = $this->getCaptcha();
        $id = $this->storeCaptcha( $captchaData );
        return new CaptchaAuthenticationRequest( $id, $captchaData );
    }
 
    public function onAuthChangeFormFields(
        array $requests, array $fieldInfo, array &$formDescriptor, $action
    ) {
        $req = AuthenticationRequest::getRequestByClass( $requests,
            CaptchaAuthenticationRequest::class );
        if ( !$req ) {
            return;
        }
 
        $formDescriptor['captchaWord'] = [
            'label-message' => null,
            'autocomplete' => false,
            'persistent' => false,
            'required' => true,
        ] + $formDescriptor['captchaWord'];
    }
 
    public function canSkipCaptcha( $user, Config $config ) {
        $allowConfirmEmail = $config->get( 'AllowConfirmedEmail' );
 
        if ( $user->isAllowed( 'skipcaptcha' ) ) {
            wfDebug( "ConfirmEdit: user group allows skipping captcha\n" );
            return true;
        }
 
        if ( $this->isIPWhitelisted() ) {
            wfDebug( "ConfirmEdit: user IP is whitelisted" );
            return true;
        }
 
        if ( $allowConfirmEmail && $user->isEmailConfirmed() ) {
            wfDebug( "ConfirmEdit: user has confirmed mail, skipping captcha\n" );
            return true;
        }
 
        return false;
    }
}